Re: 6.0 VFS/VM over-runs. Was: Apparent strange disk behaviour in 6.0

From: Peter Jeremy (peterjeremy_at_optushome.com.au)
Date: 07/29/05

  • Next message: Chris: "Re: BSD Installer release 1" 
    Date: Sat, 30 Jul 2005 07:44:50 +1000
To: Julian Elischer <julian@elischer.org>

    [CC list pruned]

    On Thu, Jul 28, 2005 at 02:13:44PM -0700, Julian Elischer wrote:
    >file data written to cache to await output to disk is allowed to grow to
    >the extent that running programs are swapped out.
    >(or at least paged out).

    I don't see this on 5.3 either. In multi-user mode (with lots of
    other processes sitting aroung idle) vmstat shows fr and sr sit at
    around 10,000/sec but there's no paging and a "ps -axl" afterwards
    shows everything mostly still resident. The active memory (avm)
    hardly changes but free memory drops from 233MB to 20MB over 8 seconds
    than oscillates between about 16MB and 30MB. Disk I/O remains at
    35-40MB/sec (ie disk limited).

    This is an Athlon XP-1800 512MB RAM writing a 10GB file onto an ATA disk.
    PREEMPTION is enabled.

    Since Marc Olzheim reports it happens with 5-STABLE and Julian reports
    it doesn't happen on 5.4 and I can't reproduce it on 5.3, one option
    would seem to be that it was MFC'd to 5 at some point since 5.4 was
    branched. Unfortunately, a quick scan through the RELENG_5 commits
    doesn't reveal anything that might be relevant.

    The other possibility is that it's RAM size related. The vmstat
    output Julian posted demonstrating the problem was on a system with a
    fair bit of RAM, but his 5.4 system is presumably smaller and my
    system definitely is. 

    -- 
Peter
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